GERM CELLS OF ARGAS 661 



of Samson ('09) for the spermatozoa of Ixodes and Ornithodoros. 

 Samson also holds the view here expressed, that the nucleus 

 marks the morphological head of the mature sperm tube, basing 

 her conclusions upon the identification of the nucleus by its 

 staining reactions and upon her studies of fertilization. After 

 many fruitless attempts she succeeded in observing the process 

 of fertilization in Ixodes and she states that it is the nuclear 

 end which first penetrates the egg. I have endeavored in vain 

 to secure similar data for Argas. 



If it be granted that the nucleus marks the morphological 

 head of the tick spermatozoon one might infer that the proto- 

 plasmic process (flagellum), which pushes outward from the 

 nuclear end of the tube at the time the spermatozoon reaches 

 maturity, is homologous with the acrosome of the other sperma- 

 tozoa. The origin of this structure is somewhat uncertain since 

 the cytoplasm of which it is composed takes no specific dye, but 

 it may not be too much to infer that it is formed largely of the 

 substance of the conspicuous finger-shaped process which is so 

 prominent a feature of the earlier stages shown in figures 25 to 

 29. This process does not migrate along the primary tube with 

 the nucleus and, although it becomes reduced in size and rela- 

 tively inconspicuous by the time the spermatozoon is trans- 

 ferred to the female, it yet persists and must later be drawn 

 into the nuclear end of the completed tube when the outer tube 

 has slipped completely back over the inner. 



The exact manner in which the spermatozoon of the fowl- 

 tick accomplishes locomotion is difficult to determine. As the 

 mitochondria-bearing end advances, its vesicular tip contracts 

 and expands in a peculiar manner and the processes surrounding 

 the vesicle are also in motion. The mitochondria within the 

 tube lie near the surface and the granules are arranged in linear 

 series, giving this portion of the tube a longitudinally striated 

 appeai'ance. One gains the impression from an examination 

 of living spermatozoa that the mitochondria represent contrac- 

 tile elements which are responsible for the movements which 

 this end of the spermatozoon exhibits. A relation between 

 mitochondria and motor organs was long ago suggested by 



